Conservation of the forest-living native birds of Mauritius

Maintaining the biodiversity of Mauritius is one of the world’s highest conservation priorities. Eight of nine surviving forest-living native bird species are threatened, yet the population limiting factors had not been convincingly diagnosed for any species, and conservation has focused on the short-term needs of the three non-passerine species. I propose an economical strategy to increase and sustain the population viability of all forest species. I studied the five threatened passerine species, especially the Mauritius Fody Foudia rubra.

These were largely associated with native forest, much of which was unoccupied by most native bird species. Although invasion of the native forest by exotic plants may reduce food availability, the previous claim that this limited the population of certain species was unsupported.

Nest predation by introduced mammals was severe. Over most of the range, recruitment could not sustain fody populations. Surplus birds from areas of higher productivity supplemented these populations. The fody distribution thus comprised source and sink areas. The richest source area was an exotic Cryptomeria japónica grove, to which nesting of the Pink Pigeon was also restricted. I argue that Cryptomeria allows concealment of nests in a habitat avoided by predatory mammals.

I propose that nest predation is the proximate factor limiting the distribution and population of the pigeon and fody and, together with habitat destruction, was the main cause of decline.

Long-term conservation requires habitat management. The existing rehabilitation strategy for mainland plant communities neglects the predator problem. To address this, habitat enhancement using selected native and exotic plants is proposed, including the creation of groves of Cryptomeria. Restoration of offshore islets, including predator eradication, would provide habitat to which threatened birds should be translocated. To maximize survival chances for all native biota, all three strategies should be pursued.